Recently, a liquid crystal display device of a lateral electric field type has been put into practical use. For example, a configuration in which gate lines are arrayed in a horizontal direction, data lines are arrayed in a vertical direction, a common electrode layer is disposed on an entire surface and a pixel electrode layer is disposed to be overlaid on the common electrode layer, on a lower transparent panel substrate, is well known. Slits parallel to the data lines are formed in the common electrode layer. An alignment film disposed on the common electrode layer is subjected to predetermined alignment treatment. In general, a direction of alignment treatment of the alignment film or an initial alignment direction of liquid crystal molecules in the OFF state is set to intersect the direction of extension of the slits at an acute angle smaller than 45°, in the liquid crystal display device of the lateral electric field type.
In this configuration, linearly polarized light incident on a display panel has a plane of vibration parallel or orthogonal to the direction of the alignment treatment, but the plane of vibration is non-parallel and non-perpendicular to line portions such as the gate lines and the data lines. For this reason, the linearly polarized light reflected on the line portions scatters and cannot keep a certain plane of vibration. Thus, light leakage may occur near the line portions and cause the contrast ratio to be lowered.
In particular, the width of a light-shielding layer disposed at a position opposite to the line portions is reduced as the pixel size becomes smaller, in a recent high-definition liquid crystal display device. If the width of a light-shielding layer is increased to suppress the light leakage near the line portions, inconvenience such as reduction in the aperture ratio of pixels may occur.